On October 16, 2023 10:01:20 AM PDT, Kees Cook <[email protected]> wrote:
>
>
>On October 15, 2023 10:47:53 PM PDT, Dan Carpenter <[email protected]>
>wrote:
>>On Sun, Oct 15, 2023 at 05:06:19PM +0200, Simon Horman wrote:
>>> On Thu, Oct 12, 2023 at 09:33:32PM +0000, Justin Stitt wrote:
>>> > strncpy() is deprecated for use on NUL-terminated destination strings
>>> > [1] and as such we should prefer more robust and less ambiguous string
>>> > interfaces.
>>> >
>>> > We expect both hi.data.modename and hi.data.drivername to be
>>> > NUL-terminated but not necessarily NUL-padded which is evident by its
>>> > usage with sprintf:
>>> > | sprintf(hi.data.modename, "%sclk,%smodem,fclk=%d,bps=%d%s",
>>> > | bc->cfg.intclk ? "int" : "ext",
>>> > | bc->cfg.extmodem ? "ext" : "int", bc->cfg.fclk,
>>> > bc->cfg.bps,
>>> > | bc->cfg.loopback ? ",loopback" : "");
>>> >
>>> > Note that this data is copied out to userspace with:
>>> > | if (copy_to_user(data, &hi, sizeof(hi)))
>>> > ... however, the data was also copied FROM the user here:
>>> > | if (copy_from_user(&hi, data, sizeof(hi)))
>>>
>>> Thanks Justin,
>>>
>>> I see that too.
>>>
>>> Perhaps I am off the mark here, and perhaps it's out of scope for this
>>> patch, but I do think it would be nicer if the kernel only sent
>>> intended data to user-space, even if any unintended payload came
>>> from user-space.
>>>
>>
>>It's kind of normal to pass user space data back to itself. We
>>generally only worry about info leaks.
>
>True but since this used to zero the rest of the buffet, let's just keep that
>behavior and use strscpy_pad().
I'm calling all byte arrays a "buffet" from now on. ;)
--
Kees Cook
